Required Snark writes: High Frequency Trading is a software engineering disaster, according to a study by the Chicago Federal Reserve. As reported at The Economic Populist, problems include:

Industry and regulatory groups have articulated best practices related to risk controls, but many firms fail to implement all the recommendations or rely on other firms in the trade cycle to catch an out-of-control algorithm or erroneous
trade. In part, this is because applying risk controls before the start of a trade can slow down an order, and high-speed trading firms are often under enormous pressure to route their orders to the exchange quickly so as to capture a trade at the desired price.

Another area of concern is that some firms do not have stringent processes for the development, testing, and deployment of code used in their trading algorithms. For example, a few trading firms interviewed said they deploy new trading strategies quickly by tweaking old code and placing it into production in a matter of minutes.

Chicago Fed staff also found that out-of-control algorithms were more common than anticipated prior to the study and that there were no clear patterns as to their cause. Two of the four clearing BDs/FCMs, two-thirds of proprietary trading firms, and every exchange interviewed had experienced one or more errant algorithms.

To sum things up, the well being of the entire world economy is now in the hands of greedy, incompetent corrupt insiders who will do anything to achieve a profit. The regulators are all off on a permanent vacation. (The Federal Reserve does not regulate HFT.) What could possibly go wrong?